Makarand (621247) writes "This article in the Chronicle describes how geothermal pumps could be used to heat our homes instead of natural gas or electricity. These pumps rely on the fact that regardless of what the surface temperature of the earth is, it is always 60 degrees a few hundred feet below. You have to drill a few holes 200 feet deep and insert U-shaped tubes in them and connect these to a heat exchanger. The tubes are filled with a solution of water and alcohol to prevent corrosion. Circulation pumps drive the water solution through the tubes in the ground and when the solution comes up from underground it is warm because it has passed through an environment of about 60 degrees.The heated liquid then is passed through the heat exchanger which takes care of the business of heating your home."